What it is
SLU-PP-332 is a synthetic small molecule, not a peptide. It activates all three estrogen-related receptor subtypes—ERRα, ERRβ, and ERRγ—with its highest potency at ERRα. These orphan nuclear receptors help regulate mitochondrial energy metabolism, fatty-acid oxidation, and the skeletal-muscle response to aerobic exercise.
Why it is called an exercise mimetic
In cultured skeletal-muscle cells, SLU-PP-332 increased cellular respiration and mitochondrial function. In mice, it activated an ERRα-dependent gene program associated with acute aerobic exercise and increased type IIa oxidative muscle fibers. The label refers to parts of that molecular and muscular adaptation program; it does not mean the compound reproduces every effect of training.
The mouse endurance result
The foundational performance study treated sedentary mice with 50 mg/kg by intraperitoneal injection twice daily for seven days. In its treadmill exhaustion test, treated mice ran about 70% longer and 45% farther than vehicle-treated mice. A two-week experiment also reported increased grip strength. Genetic experiments supported ERRα as necessary for the endurance response.
The mouse metabolic result
A follow-up study in diet-induced-obese and genetically obese mice reported higher energy expenditure and fatty-acid oxidation, reduced fat-mass accumulation, and improved insulin sensitivity. Those findings explain the interest in SLU-PP-332 for both endurance and body composition, but they remain animal outcomes.
The human evidence boundary
The published performance and metabolic experiments used mice. A later pilot study used muscle biopsies from older adults, but SLU-PP-332 was applied to isolated primary muscle cells in culture; the participants were not dosed with the compound. That work adds human-cell biology, not a human performance, pharmacokinetic, dose, or safety result.
Route and dose do not translate directly
The core mouse experiments used intraperitoneal doses measured in tens of milligrams per kilogram. My run used a fixed 500 mcg subcutaneous dose. The research does not establish how that human route and exposure compare with the mouse experiments or whether they produced meaningful ERR target engagement. A later paper developed the related compound SLU-PP-915 specifically because SLU-PP-332 lacks oral bioavailability, underscoring its status as an early research tool rather than a clinically characterized drug.
Why a higher heart rate was not a performance result
A heart-rate increase at unchanged perceived effort is an acute physiological response, but it does not demonstrate greater speed, power, endurance, or efficiency. The cited studies do not establish heart-rate elevation as a marker of ERR engagement. For this experiment, the signal mattered only if it led to a repeatable improvement in training, which it did not.
Sources
- Billon et al., ACS Chemical Biology 2023 — compound characterization, skeletal-muscle cell work, mouse oxidative-fiber changes, and treadmill endurance experiments.
- Billon et al., Journal of Pharmacology and Experimental Therapeutics 2024 — energy expenditure, fatty-acid oxidation, fat mass, and insulin sensitivity in mouse models of obesity and metabolic syndrome.
- Bonanni et al., Frontiers in Physiology 2025 — SLU-PP-332 treatment of primary human muscle cells isolated from inactive older adults, not administration to participants.
- Billon et al., Journal of Pharmacology and Experimental Therapeutics 2026 — development of orally active SLU-PP-915 and comparison with SLU-PP-332 in mice.